Ultra high frequency radio receiver



Aug. 1, 1950 G. J. LEHMANN ULTRA HIGH FREQUENCY RADIO RECEIVERV Filed Oct. 30, 1945 lll-Illu Patented Aug. 1, H1950 UN I TED STATES PATENT OFFICE ULEAHLGHFREQUENGE RIA-D10 Gerard .L Lehmann, New Yo 1k,`N Y1, assigner to International Standard Electric Corporatilpm4 New York, N. Y., a corporation offllelaware- Application October 30, 194:3, Scliaflullmlll- (Cl.` 250m-Zilli` 5 Claims.

This inventionrelates tol ultra high frequency radio receivers and amplifiers and especially to superheterodyne receivers for waves having a irequency too high for direct ampliiication,

In the highest frequency range used` for radio communication it has not yet beenI foundV practical to provide amplifiers acting directly upon the received Wave. The first tube of the receiver is therefore a frequency converter of the superheterodyne type which reduces the frequency to a value which permits amplification by standard methods:

Howeventhe tubes which are effective at these highirequencies have very small dimensionsl resulting in a necessarily low valueV forthe conversion curve. Moreover," the signals are generally transmitted*` on a` very wide frequency band. therefore the grid-circuit impedance must be very low. Consequently the4 gain in the first'` tube and the level of entry-into the intermediate frequency amplier is correspondingly low.

Thiscondition gives excessive prominence to the noise developedin the rst` tube circuits, and particularly the space current hissi in the plate circuit of the tube; a factor that-is notof particularly importantconsideration atlovverfrequencies because of the much higher grid circuit impedancesi that can be used. Under these conditions the noises originating in the rst detector tube and the intermediate,frequencycircuits acquirea rather importantgvalue; and interferegwith thesensitivity ofthereceiver;

Consequently it is importanti to impress the maximumI signalV voltage on thegrid of the' iirstl detectoremixer tube` of` the superheterodyne. Preliminary radio frequency stages or" the type usedk at lower wavelengths are not available, and attempts to increase the signal value by input inductance tunerslare subjectjtoserious mechanica-l and electrical disadvantages. An important object-oil the invention is, toprovide an `arrangement that maybe-used with ultrawhighafrequency waves that at present cannotT be directly amplifled; which willhave the eifectof'increasing the input Signalstrength to the supkerheterodynedetractor-mixer, and thereby decreasingvthe relative impmr-tanccA of the noises originatingjin thehintermediatefrequencyfcircuitsia resultw that increases materially the sensitivity ofjthezV receiver: This general accomplishedrby' providing a regenerative` action` in. the detector-mixer tube by means which is suitable for use in the indicated frequency, range.

The preferred, arrangement embodying the` in.- vcnticn, includes the use ci an ultray high4v frequency tube unit capable of oscillationl at said frequenciea the `high frequency circuit ofY the-tube including an, adjustable reactance or otherelement which can. be regulated to` maintain the tube unit. in. the neighborhood. of. but below the pointer. oscillatiom arranged, so thatunder these conditions there will be a regenerative feedback between the circuits. OL the twoelectrodes which will produce oscillation, when the reactance is given an appropriate value. An oscillator is coupled` to this tube unit4 to produce the usual heter odyning of the signal and oscillator frequencies, thecombinationwave being fed to=anintermedi` aile, frequency amplifier andthe succeeding, sections of` the4 usual superheterodyne,A circuit.

A feature of the invention, is the provision. of a novel type ottube` unitadapteclA for operation in the indicated frequency, range. Afurther, feature isthe; provision of such a unit which is `adapted for useboth as theoscillator and the. mixer.

Other features, including improved. circuitar.- rangements as Well as tube` unit constructionffeaf tures and; coupling, will appear froml the l followingr description A considered. inconnection Vwith the accompanying drawing, which is a partly schematic showing of a circuit embodying the invention,A with the tube units shown` in longitudinal central4 section The disclosed arrangement includes. a mixer unit I0 and an oscillator unit, lili. Since thel units-,are mechanically the` same, the mixer, wilLbe described, similar parts intheA oscillator being indicated by the same numerals.

The tube I2 may bean acorn triode ofthei955 type. The/cathode.v I3 is connected to a cylindri-A cal conductor I`4vthrough which the iilament leads` I5; are coaxially passed;` The grid` liis connected` to acylindrical' grid resonator I1. ccllductor Ii` and, resonator. II are concentric with and` mounted in a` cylindricah thick metal casing I8, closed at bothends, whichV providesa resonator` chambersurrounding each otthese ele. m,ents a s well as a supportforsaid elements,` `the conductor; Iggbeing seated inan end` of.` cylinder.

e I8 vvhile the grid endoi resonator I 'Iniay loesungported by a disk I9 of suitame insulating materiai The cathodeY such as polystyrene, engaging the tube end of said resonator and the casing I8.

A suitable tuning arrangement for the grid circuit is advantageously provided, including means for varying the dimensions of the chamber surrounding the grid resonator I'I. The disclosed arrangement for this purpose includes a toroidal metal member 22 spanning the space between resonator I1 and the cylinder I8, slidably engaging these elements for longitudinal adjustment. The member 22 as shown is constructed from sheet metal having inner and outer walls 23 each provided with a lateral bead 24 engaging circumferentially theadjacent portion of resonator l1 or cylinder I8, the inturned margins of the beads. being suitably spaced. Member 22 is mounted on a suitable support such as the sleeve Z5 'with a closed outer end threaded on an adjusting screw 26 having a bearing support in the end of resonator I1 at one end and at the other end extending through a bearing in the end of cylinder I8. Suitable means such as wheel 21 mounted on the outer end of screw 26 is provided for accurate longitudinal adjustment of the member n 22. An arm 23 mounted on support 25 and extending through a slot 2% in cylinder I8 prevents the support 25 and member 22 from rotating during adjustment, and also provides a convenient external index or index actuator which may move with respect to a suitable graduated scale (not shown) to indicate the wavelength to which the tube unit is tuned.

The anode 32 is connected through lead 33, which passes through a suitable opening in the wall of cylinder I8, to the input circuit 34 of the intermediate frequency amplifier 35 and thence to a grounded source of adjustable voltage 36. In the oscillator II the anode lead 33 is coupled to cylinder I8 through condenser 31, and lead 33 of course extends directly to the adjustable voltage source 36 for that unit.

A suitable coupling between the units and a connection to the antenna 4i) are provided. In the illustrated arrangement aligned lengths of coaxial line il extend into cylinders I8 with their outer ends slightly spaced and their inner conductors 42 connected to the grid resonators Il. The conductors 4I are coupled by a coaxial line 43 having an inner conductor 44 whose ends are adjustably connected to the conductors 42 to obtain `the proper coupling` The antenna 45 is connected to line 4I from mixer lil through coaxial line 45, `whose inner conductor 46 is likewise adjustable along the inner conductor 42 and may advantageously be connected to inner conductor 44 for simultaneous adjustment.

In constructing the units the dimensions of the resonant chamber surrounding the cathode resonator cylinder Il! are regulated in accordance with' the range of wavelengths to be received, which may be readily accomplished within reasonable limits by varying the length of tube I4.J The resonant ohamberhas the effect of a reactance, and the value is not critical, each value being satisfactory throughout a relatively wide band of frequencies. The oscillating circuit is of the grounded plate type in which the oscillations take place between the grid and cathodev circuits, the point Aof oscillation being determined by the potential on the anode. In the illustrated arrangement this potential `is adjusted in the oscillator to provide continuousY oscillation, and in the mixer Ill is maintained just below the point of Ioscillation, where effective feedback is ob-v tained.

One embodiment of the specific arrangement that has been described has been found to be effective in the range of 545 to 600 megacycles, corresponding to wave-lengths of 50 to 55 centimeters. Its adjustment and stability are similar to those of receivers for longer waves. By proper design of the tube units the invention is applicable to substantially shorter waves, and of course may be used effectively for wavelengths up to the length at which direct radio frequency amplication is practical. At present the upper frequency limit, above which direct radio frequency amplification is ineffective, is about 600 to 800 megacycles.

While a preferred embodiment has been shown and described, the specific disclosure thereof has been made primarily for purposes of illustration and not-limitation, since various features may be modified within the scope of the invention as set forth in the claims. The disclosed arrangement however provides a compact unit adapted for convenient and eicient construction, and an arrangement whereby two tube units may be rigidly connected by concentric lines to constitute superheterodyne input apparatus, incorporating both the oscillator and the mixer, the whole assembly being vself-contained and not subject to damage or loss'of adjustment. The means for adjusting both the wavelength and the feedback are very simple Aandv positive in action, and the unit is eflici'e'nt overfa wide bandol" wavelengths.

What is claimed is: l

l. A superheterodyne amplifier for ultra-high frequency waves comprising, in combination, a low-noisc mixer unit and an oscillator unit, each comprising a 'gridfresonator and a cathode resonator, connected respectively to the grid and cathode of an `electron discharge devicehaving also an anode, said'mixer and oscillator being of substantially lsimilar'constructiony arranged adjacent to one another, each of said resonators comprising an outer wall in the form of a cylindrical metal'casing :surrounding a tuning core, said grids and fcathodes coupled to a respective core, a coaxial linefcircuit for coupling said grid resonators, said gridresonators being in wavetransmitting relationship tosaid cathode ,resonators, with means. for varying the resonant wavelength ofdsa'idv: grid resonator. ,l

' 2. l A,- superheterodyne amplifier for `ultra-high frequencylwaves as dened in claim 1, in which said wave-transmitting relationship comprises feedback between said grid resonator and said cathode resonatonm ,3. .An I arrangement according to `claim l, wherein saidA coaxial line circuitcomprises two coaxial stubs each having an inner `and outer conductor, said inner conductors `coupled at one end to a respective tuning `core and saidA outer conductors coupled to' a `respective casing, and a coaxial*l line section lfor adjustably coupling said stubs. f

al Asuperheterodyne amplier for ultra-high frequency waves'comprisinga mixing unit and an oscillator unit feeding said mixer unit, said mixer unit, comprising an electron discharge device having cathode, grid and plate electrodes, a coaxial line gridfresonator and cathode resonator eacncor'nprilsing inner, and outer conductors, means for connecting one end of the inner conductor of ,said ygrid and cathode resonator to a grid and cathode electrode respectively, means for short circuitingsaid resonators at the other end,y saidl 'grid' resonator being. supported at said` one. @ed by. a 5.1.1111ak91,e) insulatinadisl:` mounted.

between the inner and outer conductor, and being adjustably supported at the other end by a toroidal hollow metal member spanning the space between the inner and outer conductor of said grid resonator.

5. A superheterodyne amplifier unit as defined in claim 4, in which said toroidal metal member is slidably adjusted by means of a support communicating with a suitable screw device controlled from the exterior of said resonator, and means including an arm mounted on said support and extending through a slot in said cylinder, said means preventing said member from rotating during adjustment and also providing convenient external index means adapted to indicate the wavelength to which said unit is tuned.

GERARD J. LEHMANN.

'f5 REFERENCES CITED The` following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,062,004 Hansell Nov. 24, 1936 2,067,536 Klotz Jan. 12, 1937 2,088,722 Potter Aug. 3, 1937 2,120,518 Dreyer June 14, 1938 2,227,604 Smith Jan, 7, 1941 2,236,004 MacLean Mar. 25, 1941 2,253,589 Southworth Aug. 26, 1941 2,262,979 Vilkomerson Nov. 18, 1941 2,272,062 George Feb. 3, 1942 2,277,638 George Mar. 24, 1942 2,293,151 Linder Aug. 18, 1942 2,382,954 Beaudoin Aug. 21, 1945 

